Wave Hub - The Movie

View the animation by clicking here.

Since SAS were first invited three years ago to attend meetings about the construction of a wave energy project 12 miles of the coast of St Ives, we have been pushing heavily for the possible impact it could have on the surf to be investigated.

Our challenge was taken up by scientists at the Camborne School of Mines (part of the University of Exeter in Cornwall). The report they produced on the back of their investigation has since been peer reviewed (a very lengthy process where other independent scientists read it, check its accuracy and recommend any changes) and it has now been accepted for publication in the journal Ocean Engineering. Peer review basically means that other top scientists in the field have deemed this report scientifically sound.

In their study, an advanced computer modelling package called SWAN (Simulating WAves Near-shore) was used to replicate the physical processes that occur in the real world. The Wave Hub was modelled as a 4km long partially transmitting obstacle (i.e. a barrier that removes some but not all of the wave energy that passes through it - exactly how the wave energy devices attached to the Wave Hub would behave). The model was run using nearly a years worth of wave data. In a nutshell, what they did was run the model twice, once with the Wave Hub in place, once without, and then analyses the difference.

The study was repeated using a range of energy transmission coefficients (a figure representing how much energy passes through the Wave Hub area) from 0% (i.e. no energy gets through - an impossible scenario) to 90% (only one tenth of the energy gets absorbed). This last scenario was deemed to be the most realistic estimate of what would occur at the wave hub site.

The animation shows how the predicted wave height difference changes through the 11 month period. It can be seen that the position of the wave shadow varies significantly. This is due to differences in offshore wave direction.

The results of the model suggest that if the Wave Hub was built, it would result in an average reduction in wave height at the shore of 1cm or less (a reduction of 0.31%) with a maximum reduction of 4cm (or 2.3%). The impact on wave period was so small that it was deemed negligible. As well as overall average and maximum values, data was also presented about the likely impact at several popular surfing beaches. This has been summarised in the table below.

	Average Change		Maximum Change
	Meters	%	Meters	%
Gwithian	0.01	0.36	0.02	1.08
Porthtowan	0.01	0.47	0.02	0.97
Perranporth	0.00	0.65	0.03	1.63
Fistral	0.00	0.38	0.02	1.06
Newquay Bay	0.00	0.12	0.01	0.88
Watergate Bay	0.00	0.19	0.01	0.79
Constantine Bay	0.00	0.18	0.01	1.15
Harlyn Bay	0.00	0.17	0.01	1.67

The study finally concludes by saying 'There is little cause for concern that effects introduced by the Wave Hub will be felt by shoreline users of the sea.' To paraphrase this sentence, this study suggests that any impact resulting from the Wave Hub will be of a scale so tiny that it will not be noticed by surfers.

This independent peer reviewed study should help to allay the fears that have been stirred up in the media over the last few months. Unfortunately, because getting scientific work peer reviewed is understandably a long and rigorous process, this data was not available to counter many of the unsubstantiated comments made in the press during the first few months of summer 2006.

SAS wish to thank Dean Millar, Helen Smith and Dominic Reeve for listening our concerns and carrying out this study.

Reference: Millar, D.L., Smith, H.C.M. and Reeve, D.E. (in press). Modelling analysis of the sensitivity of shoreline change to a wave farm. Ocean Engineering, available on line 24 July 2006.

Back